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    <title>Document</title>
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<body>
    <button id="submit1">发送GET请求</button>
    <button id="submit2">发送POST请求</button>
    <button id="submit3">fetch发送GET请求</button>
    <button id="submit4">fetch发送POST请求</button>
    <button id="submit5">promise+XHR封装ajax函数（post）</button>
    <script src="demo.js"></script>
</body>
</html>